L13 - Early Human Development Flashcards
Result of embryogenesis
- patterning
- definition of major acids
- definition of three germ layers (via gastrulation)
- rudiments of major organs established
Patterning
Cells acquiring identity in space and time
Major axis
Anterior/posterior
Dorsal/ventral
Three germ layers
- ectoderm (outside)
- mesoderm (between)
- endoderm (inside)
Ectodermal contributions
- all nervous tissue
- epithelium of integumentary, respiratory, digestive
(Skeletal - pharyngeal cartilage)
Mesodermal contributions
- All of:
- skeletal
- muscular
- cardiovascular
- lymphatic
Endodermis contributions
- digestive system (gut)
- respiratory epithelium (along with ectoderm)
Ecto/mesodermal contributions
- integumentary (epidermis vs. dermis/hypodermis)
Meso/endodermal contributions
- urinary (kidneys vs. bladder)
- reproductive (gonads/ducts vs. stem cell)
All germ layer contributions
Endocrine
Arrest points in oogenesis
- Prophase I (resumed during puberty)
- Metaphase II (resumed after fertilisation)
Polar bodies
Other daughter cells from meiosis that are not fertilised as all cytoplasm apportioned to one cell as it divides
- eventually gets degraded)
Path of sperm cell
- corona radiata (cells from ovary itself)
- zone pellucida
- plasma membrane of secondary oocyte
- cytoplasm of secondary oocyte
Pronuclei
Nucleus of gametes (haploid)
Cleavage
Series of relatively rapid mitotic cell division (24hrs for each cell division in humans)
Zone pellucida function
- fibrous
- prevents early implantation in Fallopian tube (which would lead to ectopic pregnancy) where a placenta cannot be formed thus no nutrient/waste exchange = death
Ectopic preganancy
Implantation of zygote outside uterus
Resulting cells from cleavage
Blastomeres
Cleavage features
Overall volume/mass of egg doesn’t increase
- instead, cells become progressively smaller as they split without growth (rapid cell division)
Blastocyst
Mammalian blastula with trophoblast & pluripotent inner cell mass instead of no inner cell mass and pluripotent blastomere/blastoderm